Safety device for electric elevators.



'No. 732,586. 4 PATENTED JUNE 30, 1903: G. T. RENNERFELT. SAFETY DEVICE FOR ELECTRIC ELEVATORS.

APPLICATION FILED SEPT. 17, 1902.

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UNITED STATES Patented June S0, 1903;

PATENT Omen.

GUSTAF T. RENNERFEL'I, OF BROOKLYN, NEW YORK, ASSIGNOR TO OTIS ELEVATOR COMPANY, OF EAST ORANGE, NEW JERSEY, A CORPORATION OF NEW JERSEY.

SAFETY DEVICE FOR ELECTRIC ELEVATORS.

SPECIFICATION forming part of Letters Patent N 0. 732,586, dated June 30, 1903.

Application filed September 17, 1902. Serial No. 123,772. (No model.)

To all whom, it may concern.-

Be it known that LGUSTAF 'I. RENNERFELT,

a subject of the King of Sweden and Norway,

and a resident of the city of New York, in the 5 borough of Brooklyn, in the county of Kings and State of New York, have invented new and useful Improvements in Safety Devices for Electric Elevators, of which the following is a specification.

It sometimes happens in electric elevators that the main circuit is opened when the motor is being driven as a generator by the load on the car or by the counterweight when that is heavier than the car and its load. On such occasions the ordinary automatic brake provided with the machinery will not act, since the electromagnet which holds it released will still be energized by the current thus generated by the motor. This is the cause of many serious accidents.

The object of my invention is to provide simple means of overcoming this difficulty and causing the machinery which moves the car to be stopped whenever the main circuit is broken.

I attain my object by providing in the circuit which controls the brake-magnet two distinct and separate paths arranged in parallel, each controlled by an independent circuit closing and opening device, which is operated in the manner hereinafter described. One of these paths is closed at all times when the motor is driving the load, but is opened whenever the motor is being driven as a generator. The other path is closed while the current is flowing through the main circuit in either direction, but is opened whenever said current ceases. Thus under the normal conditions of running at least one and some- 40 times both of said paths will be closed, and my device will have no effect on the usual operation of the brake; but if the motor is being driven as a generator and a break occurs in the main circuit both of said paths will be opened and no circuit can be made through the brake-magnet, so the latter will lose its power and the brake will be applied by the action of its spring or weight.

Referring now to the drawing, A represents the armature of the motor, B the shunt fieldcoil, and O the motor-controller. This may be of any of the well-known forms for starting and stopping and reversing the motor and may include some suitable form of switching mechanism for controlling the brake-circuit. I

D is a brake of ordinary construction ap plied by a spring or weight and released by an electromagnet or solenoid E. One end of the coil of this magnet E is connected to two contacts F and G, and the other end goes to the ordinary switch mechanism for'operating the brake in the controller 0. F and G are two additional contacts acting in conjunction with F and G, through which the brake-magnet circuit is completed to the main.

7 II and K represent two magnets, one stationary and one movable. They are shown in the drawing as a motor of which the armature K can move a certain definite distance,

its motion being limited by stops 8 s. The armature K is polarized by a current flowing in constant direction through the circuit a a. It is mechanically connected to the contactarm L, which slides over and makes electrical connection between the contacts F and F.

M is a solenoid in the main circuit, arranged to close the contacts G G when it is energized and open them when it is not energized. The circuit connections are plainly shown in the diagram--1nain circuits in heavy lines,

shunt-circuits in lighter lines.

The operation of the apparatus is as follows: As long as the motor drives the load the direction of currents in the respective circuits is as indicated by the arrow-heads. The reversal of the motor for making the car travel up or down afiects the direction of the currents onlyin the circuits between the controller and the motor. The polarity of the magnet H is such as to cause the polarized armature K to move in such direction that the contacts F F are connected bythe contact-arm L. Contacts G G are also closed by the action of the solenoid M. The solenoid E will thus receive current by two distinct and separate paths and the brake D will be released. It now the motor is driven by the load on the car, or the counterweight when that is heavier than the car and its load, so that it acts as a generator, the direction of the current flowing in the main circuit will be reversed, but willfiremain the same in the shunt-circuits. The polarity of magnet H will thus be reversed and the armature K will move in the opposite direction and move the contact-arm L ott of the contact F, so that the latter will no longer be connected to contact F, and so one'of the two paths to the brakemagnet E will be broken. The brake-magnet will still receive current by the other path through the contacts G G. If now a break should occur in the main circuit, the solenoid M will lose its power and the contacts G G will be opened. This will interrupt the other path to the brake-magnet E, so that the current will be cut off from it and the brake D will be applied and the machinery stopped. When the current reverses in the main circuit, there will be a moment when there is no current passing. For that reason the magnets K and M are so adjusted that they will not open their respective contacts F F and G G at exactly the same time. The contacts G G will be opened and closed again before the magnet K, because of its greater inertia and the time required to reverse the polarity of the field-magnet H, has opened the contacts F F.

Referring to magnets II and K, I wish to point out that the direction of movement of the magnet K depends upon the speed of the motor-armature A. If the said armature A runs so slow as to receive current from the line, the magnet K will move in such direction as to cause the contacts F F to be connected. If, on the other hand, it runs fast enough to generate current,the magnet K will move in the opposite direction and cause the contacts F F to be disconnected.

The apparatus indicated by the magnets 11 and K and the contact-arm L, short-circuiting two contacts, isillustrated and described in Patent No. 625,060, issued to me May 16, 1899, and is there used in a different combination and for a certain purpose. I now wish to claim the same apparatus in other combinations and for the purpose above described.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-- 1. In an electric elevator, the combination of a brake arranged to be released by an electromagnet, two paths for the circuit of said magnet, means for opening one of said paths when the elevator-motor is being driven as a generator, and means for opening the other of said paths when the main circuit is interrupted, substantially as described.

2. In an electric elevator, the combination of a motor and a brake, with the usual means for applying said brake and additional independent means for applying said brake auto matically when the motor is driven asa generator and the motor armature circuit is broken, substantially as described.

3. The combination with an electric motor, a source of current-supply and motor-controlling mechanism, of a brake-wheel and brake for said motor, a solenoid for operating said brake, controlled by the motor-controlling mechanism, additional means for applying the brake automatically dependent on the speed of the motor and the interruption of the main circuit, substantially as described.

4. The combination of the brake of an electric elevator with two parallel circuits in series with the winding of its releasing-magnet, electromagnetic switching mechanisms for opening one of said circuits when the elevator-motor is being driven as a generator, and the other of said circuits when the main circuit is broken, substantially as described.

5. In an electric elevator, the combination of a brake arranged to be released by an electromagnet, two paths for the circuit of said electromagnet, electromagnetic means for closing one of said paths when the elevatormotor is taking current, and opening the said path when the elevator-motor is generating current, and electromagnetic means for opening the other of said paths when the main circuit is broken, substantially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

GUSTAF T. RENNERFELT.

Witnesses:

ADOLPHUS F. HARDING, ERNEST W. MARSHALL. 

